Feature flagging, also known as feature toggling, is a powerful technique that allows developers to toggle application features on or off dynamically. It enables teams to work on new features without releasing them to all users immediately. Feature flags play a crucial role in continuous integration, A/B testing, and gradual feature rollouts. In this tutorial, we’ll explore how to use feature flags in React applications using the react-feature-flags library.

What are Feature Flags?

Feature flags are an array of objects that represent the application’s features and their activation status. Each object contains a name for the feature and a boolean isActive property.

const flags = [
  {
    name: "developmentOnly",
    isActive: true,
  },
];

To use feature flags throughout the app, we need to utilize the FlagsProvider. The FlagsProvider is a React context provider that makes the flags available as a value prop to all components in the app.

import { FlagsProvider } from "react-feature-flags";

return (
  <FlagsProvider value={flags}>
    <App />
  </FlagsProvider>
);

Controlling Rendering with Flags

By wrapping parts of the code in the Flags component, we can control whether they will be rendered or not based on the feature flags’ activation status. The Flags component takes an array of authorized flags. If any of the authorized flags have isActive set to true, the children of the Flags component will be rendered.

import { Flags } from "react-feature-flags";

return (
  <Flags authorizedFlags={["developmentOnly"]}>
    <h1>
      This title will be visible only when the "developmentOnly" flag has the
      "isActive" property set to true.
    </h1>
  </Flags>
);

Using Environment Variables for Flags

In the previous example, we hardcoded the developmentOnly flag to be true. For a more dynamic approach, we can use environment variables to set the flag’s activation status based on the current environment. If you are using React with tools like Create React App, the NODE_ENV environment variable is available during build time.

const flags = [
  {
    name: "developmentOnly",
    isActive: process.env.NODE_ENV === "development",
  },
];

Now the developmentOnly flag will be true only in development mode, ensuring that any code wrapped in it won’t affect users in production.

Feature flags are a valuable tool for controlling the activation of features based on different environments or user groups. By using feature flags, development teams can safely work on new features and gradually roll them out to users in a controlled and efficient manner.